Exposure apparatus

ABSTRACT

An exposure apparatus for printing, by exposure, a pattern of an original onto a substrate includes a housing tightly filled with a predetermined ambience and for accommodating therein at least a portion of an exposure light optical axis, and a detection system having an optical system, wherein a portion of a light path of the detection system is disposed in a first space enclosed by the housing, and wherein at least another portion of the detection system including an electrical element thereof is disposed in a second space outside the housing.

Divisional Application of application Ser. No. 09/819,673

This application is a divisional application of copending U.S. patentapplication Ser. No. 09/819,673, filed Mar. 29, 2001.

FIELD OF THE INVENTION AND RELATED ART

This invention relates to a semiconductor exposure apparatus and adevice manufacturing method for manufacturing semiconductor devices byuse of the same. In another aspect, the invention concerns asemiconductor manufacturing factory where such an exposure apparatus isprovided, and a method of performing maintenance of the exposureapparatus. Particularly, the present invention is directed to anexposure apparatus which uses short wavelength laser light such as froma fluorine excimer laser, for example.

FIG. 1 is a sectional view schematically showing the structure of aconventional exposure apparatus. Denoted in the drawing at 1 is anillumination system for projecting exposure light, and denoted at 2 is areticle having a pattern formed thereon. Denoted at 3 is a projectionoptical system for projecting the pattern of the reticle 2, and denotedat 4 is a wafer onto which the reticle pattern is to be transferred byexposure, through the projection optical system 3. Denoted at 5 is awafer stage for moving the wafer 4 to adjust the position thereof.Denoted at 6 and 7 are a reticle space and a wafer space around areticle stage and the wafer stage, respectively. In the wafer space 7,there are the wafer 4 and the wafer stage 5 as well as a detectionsystem (focus system) 8-13 for detecting the wafer surface position, forexample. Here, denoted at 8 is a measurement light source (LED), anddenoted at 9 and 12 are a light projection side lens and a lightreceiving side lens, respectively, for adjusting the focus of themeasurement light. Denoted at 10 and 11 are mirrors for adjusting thedirection of the laser. In the exposure apparatus of the structuredescribed above, the reticle space 6 and the wafer space 7 around thereticle stage and the wafer stage, respectively, are maintained at anatmospheric state, and detection systems (alignment and focus systems)are disposed in these spaces 6 and 7.

On the other hand, in recent semiconductor device manufacture, there isa growing tendency of using shorter wavelengths in the exposure lightsource of the exposure apparatus. This is because, by shortening thewavelength, the resolution of the projection exposure system used forthe exposure is improved, such that a thinner pattern can bephotoprinted. For example, since a fluorine excimer laser has a veryshort wavelength of 157 nm, the application of the same to exposureapparatuses has been attempted. The wavelength of 157 nm is in thewavelength region generally called vacuum ultraviolet. In such awavelength region, absorption of light by oxygen molecules is large and,thus, the atmosphere transmits substantially no light. Therefore, it canbe applied only in such an environment that the pressure is reducednearly to vacuum and the oxygen concentration is kept sufficiently low.According to “Photochemistry of Small Molecules” by Hideo Okabe, AWiley-Interscience Publication, 1978, page 178, the absorptioncoefficient of oxygen to light having a wavelength of 157 nm is about190 atm⁻¹cm⁻¹. This means that, when light having a wavelength of 157 nmpasses through a gas with an oxygen concentration 1% under anatmospheric pressure of one, the transmission factor T per 1 cm is onlyat the following level:T=exp(−190×1 cm×0.01 atm)=0.150.

As described, in an exposure apparatus using short wavelength laserlight such as from a fluorine excimer laser, since the absorption oflight by oxygen is large, the oxygen concentration has to be reduced andthe concentration has to be controlled strictly in order to assure asufficient transmission factor.

In conventional exposure apparatuses, however, the spaces around thereticle stage and the wafer stage are kept in an atmospheric state. If,therefore, a short wavelength laser is used, there is a possibilitythat, due to absorption by oxygen in the atmosphere, a sufficient lightquantity does not reach a wafer.

Further, when a fluorine excimer laser is used and in order that apractical exposure light irradiation amount is accomplished, the oxygenconcentration along a light path should desirably be controlled to alevel approximately not greater than 10 ppm. To this end, it isnecessary to purge the space by use of an inactive gas such as nitrogen,for example. As regards the purging means, there may be (i) a method inwhich an inactive gas is continuously purged, (ii) a method in which thespace is once evacuated to a vacuum to remove oxygen, for example, and,thereafter, it is purged, and so on. In any method, degassing fromstructural components of the exposure apparatus raises a problem.Particularly, it is very difficult to avoid oxygen from the componentsurface or from the clearance between adjacent components. It may bereduced by executing washing beforehand. However, a printed circuitboard, for example, having electrical components cannot be washed. Forthese reasons, degassing occurs gradually during the purging process,which may cause contamination of the components.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide anexposure apparatus and/or a device manufacturing method by which highresolution semiconductor devices can be produced efficiently by use ofshort wavelength exposure light.

It is another object of the present invention to provide a semiconductormanufacturing factory using such an exposure apparatus and/or amaintenance method for such an exposure apparatus.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an example of a conventional exposureapparatus.

FIG. 2 is a schematic view of an exposure apparatus according to anembodiment of the present invention.

FIG. 3 is a schematic view of an exposure apparatus according to anotherembodiment of the present invention.

FIG. 4 is a schematic view of an exposure apparatus according to afurther embodiment of the present invention.

FIG. 5 is a schematic view of a semiconductor device manufacturingsystem in an aspect thereof.

FIG. 6 is a schematic view of a semiconductor device manufacturingsystem in another aspect thereof.

FIG. 7 is a schematic view of a specific example of a user interface.

FIG. 8 is a flow chart of device manufacturing processes.

FIG. 9 is a flow chart for explaining details of a wafer process in theprocedure of the flow chart of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to the accompanying drawings.

Embodiment 1

FIG. 2 is a sectional view for schematically showing an example of asemiconductor exposure apparatus, according to the present invention,which uses an F₂ excimer laser as a light source. In the drawing,reference numerals similar to those in FIG. 1 are assigned tocorresponding elements.

In this embodiment, the wafer space 7 is isolated by a housing from theother portion. In this wafer space 7, lenses 9 and 12 and mirrors 10 and11 of an autofocus system for detecting the wafer surface position aredisposed. Focus detecting light (infrared LED having a wavelength=780nm) emitted from a light source 8 is introduced into the wafer space 7through a window 14 a made of quartz. By way of the lens 9 and themirror 10, the light is projected on the wafer 4. Then, by way of themirror 11 and the lens 12 and through another window 14 b made ofquartz, the light is imaged upon the surface of a sensor (not shown) ofa CCD detection system 13. In the wafer space 7, there are a gas inletport and a vacuum applying suction port (not shown) such that a vacuumcan be applied to the wafer space 7 by means of a vacuum pump connectedto the suction port, and that a nitrogen gas can be introduced into thespace thereafter from the gas inlet port to purge oxygen.

In accordance with this embodiment, by using a nitrogen gas, oxygen andmoisture or water content in the space between the projection opticalsystem 3 and the wafer 4 can be purged, and it assures an exposureprocess using short wavelength laser light without absorption of theexposure light by the ambient gas inside the wafer space 7. Further,since a vacuum is once applied to the wafer space 7, even if increasesduring loading or unloading of the wafer 4, it can be purged quickly.Also, in this embodiment, since a portion of the autofocus system formeasuring the wafer surface position is disposed in a space separatefrom the wafer space 7, the purity of the inside gas of the wafer space7 can be maintained at a high level. A portion of the autofocus systemto be provided outside the wafer space 7 should desirably be the CCDdetection system and the light source 8, for example, which includeelectrical components that are difficult to be washed. This arrangementeffectively reduces degassing from electrical components andcontamination due to it.

Although this embodiment uses a nitrogen gas as the purging gas, theinvention is not limited to this. Any inactive gas may be used. Forexample, helium may be used as an inactive gas.

Further, a portion of the autofocus system being provided outside may bearranged to define a space separate from the wafer space 7, and such anoutside space may be purged by a nitrogen gas, for example.

Embodiment 2

FIG. 3 is a sectional view schematically showing another embodiment of asemiconductor exposure apparatus of the present invention, which uses anF₂ excimer laser as a light source. In FIG. 3, reference numeralssimilar to those of FIG. 1 are assigned to corresponding elements.

In this embodiment, there is a TTL alignment detection system forperforming wafer alignment through a reticle and a projection opticalsystem. Measurement light therefor uses the exposure wavelength. Thereticle space 6 and a detection system space 17 are isolated from theremaining portion by housings, respectively. Inside the reticle space 6,in addition to the reticle 2, there is a portion (e.g., a lens) of adetection optical system 16 for position detection. Inside the detectionsystem space 17, in addition to the remaining portion of the detectionoptical system 16, there is a CCD detection system 15. In thisembodiment, since exposure light is used also as the alignment detectionlight, the detection system space 17 and the reticle space 6 areisolated by use of a window material of Ca F₂. The detection systemspace 17 is equipped with a gas inlet port (not shown), and the reticlespace 6 is provided with a gas inlet port and a vacuum applying suctionport (not shown). An inactive gas can be introduced through the gasinlet port, and oxygen can be purged by using nitrogen, for example.Particularly, a vacuum can be applied to the reticle space 7 by using avacuum pump connected to the suction port, and thereafter, a nitrogengas can be introduced through the gas inlet port to purge oxygen.

In accordance with this embodiment, by using a nitrogen gas, oxygen andmoisture or water content in the space between the reticle 2 and theprojection optical system 3 can be purged, and it assures an exposureprocess using short wavelength laser light without absorption of theexposure light by the ambient gas inside the reticle space 6. Further,since a vacuum is once applied to the reticle space 6, even if theoxygen concentration or water content level increases during loading orunloading of the reticle 2, it can be purged quickly. Also, in thisembodiment, since a portion of the detection optical system 16 for theposition detection is disposed in a space separate from the reticlespace 6, the purity of the inside gas of the reticle space 6 can bemaintained at a high level. A portion of the detection optical system 16to be provided outside the reticle space 6 should desirably be the CCDdetection system 15, for example, which includes electrical componentsthat are difficult to be washed. This arrangement effectively reducesdegassing from electrical components and contamination due to it.Further, since the CCD detection system 15 is disposed in the detectionsystem space 17 isolated from the reticle space 6, there is nopossibility of degassing from such electrical components orcontamination due to it.

Since, in the detection system space 17, there is no necessity ofloading or unloading a reticle, for example, a nitrogen gas may beinjected continuously to keep the oxygen concentration or the watercontent at a low level.

Although this embodiment has been described with reference to adetection optical system of a TTL alignment system, the invention is notlimited to this system. The invention is applicable also to a detectionsystem for detecting the position of an optical axis of an illuminationoptical system, for example.

Embodiment 3

FIG. 4 is a sectional view schematically showing another embodiment of asemiconductor exposure apparatus of the present invention, which uses anF₂ excimer laser as a light source. In FIG. 4, reference numeralssimilar to those of FIG. 1 are assigned to corresponding elements.

This embodiment concerns a laser interferometer as a position measuringsystem for measuring the position of a wafer.

In FIG. 4, the wafer 4 is held by a wafer chuck (not shown), which ismounted on a wafer stage 5. On the wafer stage 5, there is a mirror 22for reflecting measurement light from a laser interferometer 21. Thelaser interferometer 21 is disposed in an outside space, which isisolated from the wafer space 7. A housing 7 for tightly closing thewafer space 7 is provided with a window 23 made of quartz, through whichthe measurement light from the laser interferometer 21 can be introducedinto the wafer space 7.

As in the preceding embodiment, the wafer space 7 is provided with a gasinlet port and a vacuum applying suction port (not shown). A vacuum canbe applied to the wafer space 7 by means of a vacuum pump connected tothe suction port, and thereafter, a nitrogen gas can be introduced therefrom the inlet port, whereby oxygen in the housing 7 can be removed.

In accordance with this embodiment, by using a nitrogen gas, oxygen andmoisture or water content in the space between the projection opticalsystem 3 and the wafer 4 can be removed, and it assures an exposureprocess using short wavelength laser light without absorption of theexposure light by the ambient gas inside the wafer space 7. Further,since a vacuum is once applied to the wafer space 7, even if the oxygenconcentration or water content level increases during loading orunloading of the wafer 4, it can be purged quickly. Also, in thisembodiment, since a portion fo the position measuring system formeasuring the position of the wafer (wafer stage) is disposed in a spaceseparate from the wafer space 7, the purity of the inside gas of thewafer space 7 can be maintained at a high level. A portion of theposition measuring system to be provided outside the wafer space 7should desirably be the laser interferometer 21, for example, whichincludes electrical components that are difficult to be washed. Thisarrangement effectively reduces degassing from electrical components andcontamination due to degassing. Further, by disposing a portion of thelaser interferometer separately, a position measurement error resultingfrom the state inside the space (e.g., fluctuation) can be reduced.

Further, as in the preceding embodiment, the outside laserinterferometer, which is isolated from the wafer space may be tightlyenclosed and a nitrogen gas, for example, may be injected continuouslyinto such a closed detection system space. This effectively keeps theoxygen concentration or the water content at a low level.

Although this embodiment has been described with reference to a positionmeasuring system having a mirror mounted on a wafer stage to measure theposition of a wafer (wafer stage), the embodiment is not limited to it,as long as a laser interferometer is used. For example, the invention isapplicable also to a position measuring system having a mirror mountedon a reticle stage to measure the position of a reticle (reticle stage).

Further, the structures of the preceding embodiments maybe combinedpartially or totally.

Embodiments of Semiconductor Manufacturing System

Next, an embodiment of a manufacturing system for manufacturingsemiconductor devices such as semiconductor chips (e.g., ICs or LSIs),liquid crystal panels, CCDs, thin film magnetic heads, ormicro-machines, for example, will be described. This system is arrangedso that repair of any disorder occurring in a production machine in asemiconductor manufacturing factory or periodic maintenance thereof or,alternatively, maintenance service such as software supply can be madeby use of a computer network outside the manufacturing factory.

FIG. 5 is a schematic view of a general structure of the productionsystem, in a certain aspect thereof. Denoted in the drawing at 101 is abusiness office of a vendor (machine supplying maker) for providingsemiconductor device manufacturing apparatuses. As examples of suchproduction machines, here, pre-process machines (various lithographicapparatuses such as exposure apparatuses, resist coating apparatus,etching apparatuses, for example, and heat treatment apparatuses, filmforming apparatuses, and flattening apparatuses) and post-processmachines (assembling machines or inspection machines, for example) areexpected. Inside the business office 101, there are a host controlsystem 108 for providing a maintenance database for the productionmachines, plural operating terminal computers 110, and a local areanetwork (LAN) 109 for connecting these computers to constitute anintranet. The host control system 108 is provided with a gateway forconnecting the LAN 109 to an internet 105, which is an outside networkof the office, and a security function for restricting the access fromthe outside.

On the other hand, denoted at 102-104 are manufacturing factories of asemiconductor manufacturer or manufacturers as a user (users) ofproduction machines. The factories 102-104 may be those belonging todifferent manufacturers or the same manufacturer (e.g., pre-processfactory and post-process factory). In each of the factories 101-104,there are production machines 106, a local area network (LAN) 111 forconnecting them to constitute an intranet, and a host control system 107as a monitoring system for monitoring the state of operation of theproduction machines 106. The host control system 107 in each factory102-104 is provided with a gateway for connecting the LAN 111 in thefactory to the internet 105, which is an outside network of the factory.With this structure, the host control system 108 of the vendor 1101 canbe accessed from the LAN 111 in each factory, through the Internet 105.Through the security function of the host control system 108, onlyadmitted users can gain access thereto. More specifically, through theinternet 105, status information representing the state of operation ofthe production machines 106 (for example, the state of the machine inwhich any disorder has occurred) may be transmitted as a notice from thefactory to the vendor. Additionally, response information responsive tothe notice (for example, information on how the disorder should betreated or software data concerning the treatment) as well as latestsoftware and maintenance information such as help information may besupplied from the vendor. The data communication between each factory102-104 and the vendor 101 as well as the data communication through theLAN 111 in each factory may use a communication protocol (TCP/IP)generally used in the internet. In place of using the internet, anexclusive line network (e.g., ISDN) having higher security in which nothird party can access, may be used. Further the host control system isnot limited to the system as provided by the vendor. A database may bestructured by the user and set in an outside network, such that it canbe accessed from plural user factories.

FIG. 6 is a schematic view of the general structure of the productionsystem according to this embodiment, in another aspect thereof differentfrom FIG. 5. In the preceding example, plural user factories each havingproduction machines and the control system of the vendor of theproduction machine are connected through an external network, so thatthrough this external network, information related to the productioncontrol in each factory or related to at least one production machine isdata communicated. In this example, as compared therewith, a factoryhaving production machines from different vendors and control systems ofthe vendors corresponding to the user production machines are connectedwith each other through an external network outside the factory, so thatmaintenance information for these production machines is datacommunicated.

Denoted in the drawing at 201 is a manufacturing factory of a productionmachines user (e.g., a semiconductor device manufacturer). Along theproduction line in the factory, there are many production machines forperforming various processes, that is, in this example, exposureapparatus 201, resist processing apparatus 203, and film formationprocessing apparatus 204 introduced. Although in the drawing only onefactory is illustrated, in practice, plural factories may be arrangedinto the network. Each production machine in the factory is connectedthrough a LAN 206 to constitute an intranet. The operation of theproduction line is controlled by a host control system 205.

On the other hand, in the business offices of vendors (e.g., a machinesupplying maker) such as an exposure apparatus manufacturer 210, aresist processing machine manufacturer 220, and a film forming machinemanufacturer 230, for example, there are host control system 211, 221and 231 for performing remote control maintenance of the machinessupplied by them. Each of these host control system is equipped with amaintenance database and a gateway for the outside network. The hostcontrol system 205 for controlling machines in the user factory and thecontrol systems 211, 221 and 231 of the machine vendors are connectedwith each other through the external network 200 (internet) or anexclusive line network. If, in this production system, a disorder occursin any one of the production machines in the production line, theoperation of the production machine is stopped. However, this can be metquickly through the remote control maintenance of the disordered machinefrom the machine vendor by way of the internet 200. Therefore, thesuspension of the production line can be made minimum.

Each of the production machines in the factory may have a display, anetwork interface and a computer for executing network accessingsoftware stored in a storage device as well as machine operatingsoftware. The storage device may be a memory or a hard disk or,alternatively, a network file server. The network accessing software mayinclude an exclusive or wide-use web browser, and a user screeninterface such as shown in FIG. 7, for example, is provided on thedisplay. Various information may be inputted into the computer (inputitems on the screen) by an operator or operators who control theproduction machines in the factory, such as, for example, machine type(401), serial number (402), trouble file name (403), date of disorder(404), emergency level (405), status (406), solution or treatment (407),and progress (408). The thus inputted information is transmitted to themaintenance database through the internet. In response, appropriatemaintenance information is replied from the maintenance database to theuser display. Further, the user interface as provided by the web browserenables a hyperlink function (410-412) as illustrated. As a result, theoperator can access further details of information in each of the items,can get latest version software to be used for the production machine,from the software library provided by the vendor, or can get anoperation guide (help information) for the factory operators.

Next, a semiconductor device manufacturing process, which uses theproduction system described above, will be explained.

FIG. 8 is a flow chart of a general procedure for manufacturingsemiconductor devices.

Step 1 is a design process for designing a circuit of a semiconductordevice. Step 2 is a process for making a mask on the basis of thecircuit pattern design. Step 3 is a process for preparing a wafer byusing a material such as silicon. Step 4 is a wafer process (called apre-process) wherein, by using the so prepared mask and wafer, circuitsare practically formed on the wafer through lithography. Step 5subsequent to this is an assembling step (called a post-process) whereinthe wafer having been processed by step 4 is formed into semiconductorchips. This step includes an assembling (dicing and bonding) process anda packaging (chip sealing) process. Step 6 is an inspection step whereinan operation check, a durability check and so on for the semiconductordevices provided by step 5, are carried out. With these processes,semiconductor devices are completed and they are shipped (step 7).

The pre-process and the post-process may be performed in separateexclusive factories. In each factory, the maintenance is carried out onthe basis of the remote maintenance system described hereinbefore.Further, between the pre-process factory and the post-process factory,data communication of information related to the production control andmachine maintenance may be done through the internet or an exclusiveline network.

FIG. 9 is a flow chart showing details of the wafer process.

Step 11 is an oxidation process for oxidizing the surface of a wafer.Step 12 is a CVD process for forming an insulating film on the wafersurface. Step 13 is an electrode forming process for forming electrodesupon the wafer by vapor deposition. Step 14 is an ion implanting processfor implanting ions to the wafer. Step 15 is a resist process forapplying a resist (photosensitive material) to the wafer. Step 16 is anexposure process for printing, by exposure, the circuit pattern of themask on the wafer through the exposure apparatus described above. Step17 is a developing process for developing the exposed wafer. Step 18 isan etching process for removing portions other than the developed resistimage. Step 19 is a resist separation process for separating the resistmaterial remaining on the wafer after being subjected to the etchingprocess. By repeating these processes, circuit patterns are superposedlyformed on the wafer.

Since the machines used in these processes are maintained through aremote maintenance system as described above, disorders may be preventedbeforehand. If there occurs a disorder, it can be met quickly.Therefore, the device productivity can be improved significantly.

In accordance with the embodiments described hereinbefore, degassingfrom a detection system can be reduced, and degradation of thetransmission factory of an optical system such as a projection lens or adetection system can be prevented effectively. Further, the need fortaking some measures for providing a vacuum in an electrical system canbe removed.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

1. An exposure apparatus for printing, by exposure, a pattern of anoriginal on a substrate, said apparatus comprising: a housing tightlyfilled with a predetermined ambience and for accommodating therein atleast a portion of an exposure light optical axis; and a detectionsystem having an optical system, wherein a portion of a light path ofsaid detection system is disposed in a first space enclosed by saidhousing, and wherein at least another portion of said detection systemincluding an electric element thereof is disposed in a second spaceoutside said housing. 2-24. (canceled)